1. Field
The disclosure relates to a heterocyclic derivative, and more particularly to a carbazole derivative applied to organic light emitting diodes.
2. Description of the Related Art
An organic light emitting diode (OLED) has been deemed as a rising star of the flat panel display or lighting industry due to its excellent characteristics including light weight, thin profile, self-luminescence, low power consumption, no backlight requirement, no view angle limitation and high response rate etc. Considering the luminescence mechanism of phosphorescent materials in OLED devices, in order to achieve the best luminescence efficiency and quantum efficiency, the host materials with proper energy levels are required. Among them, blue phosphorescent host materials need a larger energy level gap, and such qualified molecules should have a shorter conjugated system, in addition, the thermal stability possessed by the host materials should also be considered. Therefore, the structural design for such host materials will be of corresponding difficulty. Most traditional commercially available host materials or those academically published for phosphorescent OLED devices are the derivatives containing carbazole fragments or multiple phenyl silicon functional groups. However, the known materials have problems of poor thermal stability or low current density resulting in over voltage. Therefore, development of host materials suitable for application to blue phosphorescent OLED devices is a very important topic.